U.S. patent application number 10/633371 was filed with the patent office on 2005-02-03 for spinal implant.
Invention is credited to Mitchell, Margaret E., Moreno, Anthony P., Smith, Aaron C., Webb, Scott A..
Application Number | 20050027360 10/633371 |
Document ID | / |
Family ID | 34104582 |
Filed Date | 2005-02-03 |
United States Patent
Application |
20050027360 |
Kind Code |
A1 |
Webb, Scott A. ; et
al. |
February 3, 2005 |
Spinal implant
Abstract
A spinal implant may be used to stabilize a portion of a spine.
The implant may promote bone growth between adjacent vertebrae that
fuses the vertebrae together. An implant may include an opening
through a height of a body of the implant. The body of the implant
may include curved sides. A top and/or a bottom of the implant may
include protrusions that contact and/or engage vertebral surfaces
to prevent backout of the implant from the disc space. A variety of
instruments may be used to prepare a disc space and insert an
implant. The instruments may include, but are not limited to, a
distractor, a rasp, and one or more guides. The implant and
instruments may be supplied in an instrument kit.
Inventors: |
Webb, Scott A.; (Lago,
FL) ; Moreno, Anthony P.; (Tarpon Springs, FL)
; Mitchell, Margaret E.; (Cedar Park, TX) ; Smith,
Aaron C.; (Arlington, TN) |
Correspondence
Address: |
MEYERTONS, HOOD, KIVLIN, KOWERT & GOETZEL, P.C.
P.O. BOX 398
AUSTIN
TX
78767-0398
US
|
Family ID: |
34104582 |
Appl. No.: |
10/633371 |
Filed: |
August 1, 2003 |
Current U.S.
Class: |
623/17.11 |
Current CPC
Class: |
A61F 2002/30922
20130101; A61F 2250/0037 20130101; A61F 2310/00359 20130101; A61F
2/28 20130101; A61F 2230/0063 20130101; A61F 2250/0006 20130101;
A61F 2002/2835 20130101; A61F 2/4465 20130101; A61F 2002/3082
20130101; A61F 2230/0015 20130101; A61F 2002/30133 20130101; A61F
2310/00796 20130101; A61B 2090/062 20160201; A61F 2002/30894
20130101; A61F 2250/0098 20130101; A61F 2/4603 20130101; A61F
2002/30326 20130101; A61F 2002/4635 20130101; A61F 2310/00023
20130101; A61B 17/1671 20130101; A61F 2002/30538 20130101; A61B
17/1659 20130101; A61B 2017/0256 20130101; A61F 2002/3008 20130101;
A61F 2310/00179 20130101; A61F 2002/30308 20130101; A61F 2/4611
20130101; A61F 2310/00407 20130101; A61F 2002/30677 20130101; A61F
2002/30324 20130101; A61F 2002/30604 20130101; A61F 2002/4627
20130101; A61F 2250/0036 20130101; A61F 2002/30616 20130101; A61F
2002/30059 20130101; A61F 2310/00017 20130101; A61F 2002/30593
20130101; A61F 2210/0004 20130101; A61F 2002/30062 20130101; A61F
2002/30787 20130101; A61F 2002/30904 20130101 |
Class at
Publication: |
623/017.11 |
International
Class: |
A61F 002/44 |
Claims
1. A spinal implant, comprising: a top, wherein at least a portion
of the top is configured to contact a first vertebra; a bottom,
wherein at least a portion of the bottom is configured to contact a
second vertebra; a curved anterior side; a curved posterior side;
and an opening extending through the spinal implant from the top to
the bottom.
2. The spinal implant of claim 1, further comprising a proximal
end, wherein the proximal end is substantially flat.
3. The spinal implant of claim 1, further comprising a proximal
end, wherein the proximal end is substantially rounded.
4. The spinal implant of claim 1, further comprising a distal end,
wherein the distal end is tapered.
5. The spinal implant of claim 1, further comprising a distal end,
wherein the distal end is curved.
6. The spinal implant of claim 1, wherein the top comprises one or
more protrusions configured to contact the first vertebra.
7. The spinal implant of claim 1, wherein the top comprises
protrusions configured to contact the first vertebra, and wherein
at least two of the protrusions differ in height.
8. The spinal implant of claim 1, wherein the top comprises
protrusions configured to contact the first vertebra, and wherein
the protrusions are in a radial pattern.
9. The spinal implant of claim 1, wherein the top comprises
protrusions configured to contact the first vertebra, and wherein
at least two of the protrusions differ in shape.
10. The spinal implant of claim 1, wherein the top comprises
protrusions configured to contact the first vertebra, and wherein a
first spacing between a first pair of adjacent protrusions differs
from a second spacing between a second pair of adjacent
protrusions.
11. The spinal implant of claim 1, wherein the bottom comprises one
or more protrusions configured to contact the second vertebra.
12. The spinal implant of claim 1, wherein the bottom comprises
protrusions configured to contact the second vertebra, and wherein
at least two of the protrusions differ in height.
13. The spinal implant of claim 1, wherein the bottom comprises
protrusions configured to contact the second vertebra, and wherein
the protrusions are in a radial pattern.
14. The spinal implant of claim 1, wherein the bottom comprises
protrusions configured to contact the second vertebra, and wherein
at least two of the protrusions differ in shape.
15. The spinal implant of claim 1, wherein the bottom comprises
protrusions configured to contact the second vertebra, and wherein
a first spacing between a first pair of adjacent protrusions
differs from a second spacing between a second pair of adjacent
protrusions.
16. The spinal implant of claim 1, wherein an inner surface of the
anterior side comprises one or more projections extending into the
opening, and wherein the one or more projections are configured to
strengthen the implant.
17. The spinal implant of claim 1, wherein an inner surface of the
posterior side comprises one or more projections extending into the
opening, and wherein the one or more projections are configured to
strengthen the implant.
18. The spinal implant of claim 1, wherein at least one of the
sides comprises a recess configured to engage an insertion
instrument.
19. The spinal implant of claim 1, wherein at least one of the
sides comprises a groove configured to engage an insertion
instrument.
20. The spinal implant of claim 1, wherein the anterior side
comprises a first groove, wherein the posterior side comprises a
second groove, and wherein the grooves are configured to engage an
insertion instrument.
21. The spinal implant of claim 1, further comprising a proximal
end, and wherein the proximal end comprises one or more grooves
configured to engage an insertion instrument.
22. The spinal implant of claim 1, further comprising a distal end,
and wherein the distal end comprises one or more grooves configured
to engage an insertion instrument.
23. The spinal implant of claim 1, further comprising one or more
openings extending through the anterior side.
24. The spinal implant of claim 1, further comprising one or more
openings extending through the posterior side.
25. The spinal implant of claim 1, further comprising one or more
openings extending through the anterior side and one or more
openings extending through the posterior side, and wherein at least
one of the anterior side openings aligns with at least one of the
posterior side openings to allow for monitoring of bone growth
through the implant.
26. The spinal implant of claim 1, wherein the spinal implant
comprises bone.
27. The spinal implant of claim 1, wherein the spinal implant
comprises polyether ether ketone.
28. The spinal implant of claim 1, wherein the spinal implant
comprises one or more openings for X-ray sensitive material.
29. The spinal implant of claim 1, wherein the spinal implant
comprises metal.
30. The spinal implant of claim 1, wherein the spinal implant
comprises titanium.
31. The spinal implant of claim 1, wherein the top is treated to
promote osseointegration of the implant with bone.
32. The spinal implant of claim 1, wherein the top is roughened to
promote fusion of the spinal implant with bone.
33. The spinal implant of claim 1, wherein the opening is
configured to receive packing material.
34. The spinal implant of claim 1, further comprising packing
material placed in the opening, and wherein the packing material
comprises bone.
35. The spinal implant of claim 1, further comprising packing
material placed in the opening, wherein the packing material
comprises synthetic bone material.
36. A spinal implant, comprising: a body, wherein the body
comprises: a top comprising radially positioned protrusions,
wherein the top protrusions are configured to contact a first
vertebra; a bottom comprising radially positioned protrusions,
wherein the bottom protrusions are configured to contact a second
vertebra; a curved anterior side; a curved posterior side; and an
opening extending through the body from the top to the bottom.
37. The spinal implant of claim 36, wherein the top protrusions
near the anterior side are coarser than the top protrusions near
the posterior side.
38. The spinal implant of claim 36, wherein the bottom protrusions
near the anterior side are coarser than the bottom protrusions near
the posterior side.
39. The spinal implant of claim 36, wherein at least two of the top
protrusions differ in height.
40. The spinal implant of claim 36, wherein at least two of the top
protrusions differ in shape.
41. The spinal implant of claim 36, wherein a first spacing between
a first pair of adjacent top protrusions differs from a second
spacing between a second pair of adjacent top protrusions.
42. The spinal implant of claim 36, wherein at least two of the
bottom protrusions differ in height.
43. The spinal implant of claim 36, wherein at least two of the
bottom protrusions differ in shape.
44. The spinal implant of claim 36, wherein a first spacing between
a first pair of adjacent bottom protrusions differs from a second
spacing between a second pair of adjacent bottom protrusions.
45. The spinal implant of claim 36, wherein the top protrusions
near the posterior side of the body are larger than the top
protrusions near the anterior side of the body.
46. The spinal implant of claim 36, wherein the top protrusions
near the posterior side of the body are higher than the top
protrusions near the anterior side of the body.
47. The spinal implant of claim 36, wherein the bottom protrusions
near the posterior side of the body are larger than the bottom
protrusions near the anterior side of the body.
48. The spinal implant of claim 36, wherein the bottom protrusions
near the posterior side of the body are higher than the bottom
protrusions near the anterior side of the body.
49. A spinal implant, comprising: a body, wherein the body
comprises: a curved anterior side; a curved posterior side; a top
comprising protrusions, wherein the top protrusions near the
anterior side are finer than the top protrusions near the posterior
side; a bottom; and an opening extending through the body from the
top to the bottom.
50. The spinal implant of claim 49, wherein the bottom further
comprises protrusions, and wherein the bottom protrusions near the
anterior side are finer than the bottom protrusions near the
posterior side.
51. The spinal implant of claim 49, wherein the bottom further
comprises protrusions, and wherein the bottom protrusions near the
anterior side are coarser than the bottom protrusions near the
posterior side.
52. The spinal implant of claim 49, wherein the bottom further
comprises protrusions, wherein the bottom protrusions near the
anterior side comprise a first radial pattern, and wherein the
bottom protrusions near the posterior side comprise a second radial
pattern.
53. The spinal implant of claim 49, wherein the top protrusions
near the anterior side comprise a radial pattern.
54. The spinal implant of claim 49, wherein the top protrusions
near the posterior side comprise a radial pattern.
55. The spinal implant of claim 49, wherein the bottom further
comprises protrusions, wherein the bottom protrusions near the
anterior side are coarser than the bottom protrusions near the
posterior side.
56. The spinal implant of claim 49, further comprising one or more
openings extending through the anterior side.
57. The spinal implant of claim 49, further comprising one or more
openings extending through the posterior side.
58. The spinal implant of claim 49, further comprising one or more
openings extending through the anterior side and one or more
openings extending through the posterior side, and wherein at least
one of the anterior side openings aligns with at least one of the
posterior side openings to allow monitoring of bone growth through
the body.
59. A rasp, comprising: an outer shaft; an inner shaft extending
through the outer shaft; an end member pivotably coupled to the
distal end of the inner shaft; and wherein a distal end of the
outer shaft is configured to engage a proximal end of the end
member.
60-73. (cancelled)
74. A method, comprising: inserting an end member of a rasp between
portions of bone, wherein the end member is secured at a first
angle relative to a shaft of the rasp; loosening the end member
relative to the shaft of the rasp; pivoting the end member relative
to the shaft of the rasp; securing the end member at a second angle
relative to the shaft of the rasp; and abrading at least one of the
bone portions with the end member of the rasp.
75. An implant inserter, comprising: an outer shaft; an inner shaft
extending through the outer shaft; arms coupled to a distal end of
the inner shaft; and wherein the outer shaft is configured to
engage the arms.
76-85. (cancelled)
86. An instrumentation kit, comprising: a cutting edge distractor;
a rasp with a pivotable end member; an implant inserter; and one or
more guides.
87. A spinal implant kit, comprising: spinal implants, wherein the
implants comprise a range of heights and lordotic angles; a rasp
with a pivotable end member; an implant inserter; and one or more
guides.
88. A method, comprising: inserting a rasp in a disc space between
vertebrae; abrading the vertebrae with the rasp, wherein the rasp
comprises a pivotable end member; and positioning a spinal implant
coupled to an implant inserter between the vertebrae using a
guide.
89-95. (cancelled)
Description
BACKGROUND
[0001] 1. Field of Invention
[0002] The present invention generally relates to the field of
medical devices. Some embodiments of the invention relate to spinal
implants inserted in patients during surgical procedures and to
instruments used to insert the implants. Some embodiments of the
invention relate to instruments for preparing a space for an
implant. Other embodiments of the invention relate to methods for
positioning an implant during a surgical procedure.
[0003] 2. Description of Related Art
[0004] An intervertebral disc may degenerate. Degeneration may be
caused by trauma, disease, and/or aging. An intervertebral disc
that becomes degenerated may have to be partially or fully removed
from a spinal column. Partial or full removal of an intervertebral
disc may destabilize the spinal column. Destabilization of a spinal
column may result in alteration of a natural separation distance
between adjacent vertebrae. Maintaining the natural separation
between vertebrae may prevent pressure from being applied to nerves
that pass between vertebral bodies. Excessive pressure applied to
the nerves may cause pain and/or nerve damage. During a spinal
fixation procedure, a spinal implant may be inserted in a space
created by the removal or partial removal of an intervertebral disc
between adjacent vertebrae. The spinal implant may maintain the
height of the spine and restore stability to the spine. Bone growth
may fuse the implant to adjacent vertebrae.
[0005] A spinal implant may be inserted during a spinal fixation
procedure using an anterior, lateral, posterior, or transverse
spinal approach. A discectomy may be performed to remove or
partially remove a defective or damaged intervertebral disc. The
discectomy may create a space for a spinal implant. The amount of
removed disc material may correspond to the size and type of spinal
implant to be inserted.
[0006] Spinal surgery may be complex due in part to the proximity
of the spinal cord and/or the cauda equina. Preparation instruments
and spinal implants may need to be carefully inserted to avoid
damage to nerve tissue. Alignment and spacing of a spinal implant
that is to be inserted into a patient may be determined before
surgery. Achieving the predetermined alignment and spacing during
surgery may be important to achieve optimal fusion of adjacent
vertebrae.
[0007] Bone graft and/or bone implants may be used to promote bone
growth that will fuse vertebrae together. Bone graft may be
autogenic bone, allogenic bone, synthetic material, xenogenic bone
or combinations thereof. Autogenic bone is bone obtained from
another location of a patient. Allogenic bone is bone derived from
the same species as the patient. Xenogenic bone is bone derived
from a species other than that of the patient. Implants may be
formed of metal, polymers, ceramics, inorganic compositions,
autogenic bone, allogenic bone, xenogenic bone, or combinations
thereof.
[0008] Spinal implants are described in U.S. Pat. No. 5,653,763 to
Errico et al.; U.S. Pat. No. 5,713,899 to Marney et al.; U.S. Pat.
No. 6,143,033 to Paul et al.; U.S. Pat. No. 6,245,108 to Biscup;
and U.S. Pat. No. 5,609,635 to Michelson, all of which are
incorporated by reference herein as if fully set forth herein.
SUMMARY
[0009] A spinal implant may be used to provide stability and
promote fusion of adjacent vertebrae. The implant may be used in
conjunction with a spinal stabilization device such as a bone plate
or rod-and-fastener stabilization system. The implant may establish
a desired separation distance between vertebrae. The implant may
promote bone growth between adjacent vertebrae that fuses the
vertebrae together. An instrumentation kit may include instruments
and implants necessary for insertion of an implant in a
patient.
[0010] Implants may be constructed of biocompatible materials
sufficiently strong to maintain spinal distraction. Implants may
include, but are not limited to, allograft bone, xenograft bone,
autograft bone, metals, ceramics, inorganic compositions, polymers,
or combinations thereof. If the implant is not made of bone,
surfaces of the implant that contact bone may be treated to promote
fusion of the implant to the bone. Treatment may include, but is
not limited to, applying a hydroxyapatite coating on contact
surfaces, spraying a titanium plasma on contact surfaces, and/or
texturing the contact surfaces by scoring, peening, implanting
particles in the surfaces, or otherwise roughening the
surfaces.
[0011] In some embodiments, an implant may include an opening that
extends through a height of the implant. The opening may have a
regular shape or an irregular shape. Bone graft may be placed in
the opening. The bone graft may be autogenic bone graft, allogenic
bone graft, xenogenic bone graft, and/or synthetic bone graft. Some
implant embodiments may be constructed from allogenic bone, such as
cortical bone from a femur, tibia, or other large bone. In some
embodiments, an implant may be formed from one or more pieces of
allograft bone cut to a desired shape.
[0012] In certain embodiments, sides of an implant may be shaped to
increase contact between an implant and adjacent vertebrae.
Increasing contact of an implant with adjacent vertebrae may
inhibit movement of the implant after insertion. An increased
contact area between an implant and adjacent vertebrae may promote
bone growth between adjacent vertebrae. In some embodiments, one or
more sides of an implant may be curved. One or more curved sides of
an implant may allow the implant to be maneuvered in a disc space
during insertion of the implant. The curvature of a side may
approximate a curvature of an anterior side of a vertebra adjacent
to which the implant is inserted.
[0013] In certain embodiments, an implant may have one or more
passages extending from an outer side of a body of the implant to
an inner side of the body. The passages may communicate with a
central opening in the implant. The passages may facilitate
insertion of packing material in the central opening. In certain
embodiments, one or more projections may extend from an inner side
of the body into the central opening. The projections may be
substantially the same height as the implant. Dimensions of a
projection may be chosen to strengthen the implant without
significantly decreasing the size of the central opening.
[0014] In some embodiments, an outer side of an implant may include
a groove near the proximal end and/or the distal end of the body.
The groove may be designed to receive an instrument to facilitate
insertion of the implant in an intervertebral disc space.
[0015] A top and/or a bottom of an implant may include protrusions.
The protrusions may engage vertebral surfaces. Protrusions may
inhibit backout of the implant from the vertebrae. The protrusions
may form a radial pattern. In some embodiments, one or more
protrusions may have the same height, width, and/or spacing. In
certain embodiments, one or more protrusions may have different
heights, widths and/or spacing.
[0016] Instruments may be used to prepare a space for an implant
between adjacent vertebrae. An instrument may be used to insert an
implant in a prepared space. Instruments may be supplied to a
surgeon or surgical team in an instrument set. An instrument set
may include one or more implants for use during an insertion
procedure. An instrument set may include implants of various sizes
and/or lordotic angles to allow selection of an implant to suit a
patient during surgery.
[0017] An instrumentation set may include one or more distractors.
In some embodiments, a distractor may be fixed-tip distractor. A
tip of the distractor may include a narrow dimension and a wide
dimension. In some embodiments, one or more surfaces of a tip of a
distractor may be convex. A distractor tip with a convex surface
may reduce trauma to a surgical site during distraction of
vertebrae. In certain embodiments, a tip of the distractor may
include cutting surfaces.
[0018] An instrumentation set may include a rasp to abrade a
vertebral surface before insertion of an implant in a disc space.
In some embodiments, a rasp may include an end member pivotably
coupled to an inner shaft of the rasp. An angle of the end member
relative to the inner shaft may be varied as the rasp is moved
through the disc space.
[0019] An instrumentation set may include an implant inserter. The
implant inserter may be used to grasp sides of an implant. After
insertion of the implant, the implant may be released from the
inserter without the application of significant rotational forces
to the implant. The implant inserter may have a low profile that
allows for visualization of the implant and surrounding area during
insertion of the implant.
[0020] A discectomy may be performed to establish a disc space
between vertebrae. The disc space may be prepared for implant
insertion by distraction of adjacent vertebrae. In some
embodiments, a rasp may be inserted in a disc space to remove
osteophytes and/or to smooth the vertebral surfaces. Abrasion of
the vertebral surfaces may promote contact between the implant and
the vertebrae. An angle of an end member of the rasp may be
adjusted as the rasp is moved through the disc space to abrade the
vertebrae. The rasp may be removed from the disc space and a first
guide may be inserted in the disc space. An implant coupled to an
implant inserter may be placed proximate the first guide and guided
into the disc space using a transverse approach along the surface
of the first guide. The implant may be removed from the implant
inserter. A second guide may be inserted in the disc space near the
proximal end of the implant. The first and second guides may be
used together to position the implant in the disc space. The first
and second guides may be removed from the disc space.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Advantages of the present invention will become apparent to
those skilled in the art with the benefit of the following detailed
description and upon reference to the accompanying drawings in
which:
[0022] FIG. 1 depicts a perspective view of an embodiment of a
spinal implant.
[0023] FIG. 2 depicts a view of the posterior side of an embodiment
of a spinal implant.
[0024] FIG. 3 depicts a top view of an embodiment of a spinal
implant.
[0025] FIG. 4 depicts a perspective view of an embodiment of a
fixed-tip distractor.
[0026] FIG. 5 depicts a side view of an embodiment of a fixed-tip
distractor.
[0027] FIGS. 6A and 6B depict end views of embodiments of a
fixed-tip distractor.
[0028] FIG. 7 depicts a front view of an embodiment of a rasp.
[0029] FIG. 8 depicts a perspective view of an embodiment of an end
member of a rasp.
[0030] FIG. 9 depicts a front view of an embodiment of a pivoted
end member of a rasp.
[0031] FIG. 10 depicts a perspective view of an embodiment of a
guide.
[0032] FIG. 11 depicts a front view of an embodiment of an implant
inserter.
[0033] FIG. 12 depicts a front view of an embodiment of a
guide.
[0034] FIGS. 13A-13D depict schematic views during insertion of a
spinal implant in a disc space.
[0035] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of example in the drawings and will herein be described in
detail. The drawings may not be to scale. It should be understood
that the drawings and detailed description are not intended to
limit the invention to the particular form disclosed, but on the
contrary, the intention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the present
invention as defined by the appended claims.
DETAILED DESCRIPTION
[0036] An intervertebral disc implant may be used to stabilize a
portion of a spine. The disc implant may replace all or a portion
of an intervertebral disc that has degenerated due to natural wear,
trauma, or disease. The implant may restore a normal separation
distance between adjacent vertebrae and promote fusion of the
vertebrae.
[0037] FIG. 1 depicts a perspective view of implant 100. Implant
100 may include body 110. Body 110 may include opening 112. Opening
112 may extend completely or partially through a height of body
110. A cross-sectional shape of opening 112 may be, but is not
limited to, circular, oval, square, rectangular, or irregular. In
certain embodiments, opening 112 may be kidney shaped.
[0038] Body 110 of implant 100 may include posterior side 114 and
anterior side 116. Sides 114, 116 of implant 100 may be curved. In
some embodiments, the curvature of posterior side 114 may be
substantially the same as the curvature of anterior side 116. In
some embodiments, the curvature of posterior side 114 may be
different than the curvature of anterior side 116. In some
embodiments, posterior side 114 may have a smaller radius of
curvature than anterior side 116. A curvature of anterior side 116
may approximate a curvature of an anterior side of a vertebra
adjacent to which the implant is inserted. Curvature of posterior
side 114 may allow implant 100 to be maneuvered in the disc space
during transverse insertion of the implant.
[0039] In certain embodiments, body 110 of implant 100 may have one
or more passages extending through sides 114, 116 substantially
perpendicular to opening 112 of the body. A cross-sectional shape
of one of the passages may be, but is not limited to, circular,
oval, square, rectangular, or irregular. FIG. 1 depicts sides 114,
116 with passages 118. Passages 118 may communicate with opening
112. Passages 118 may facilitate insertion of packing material in
opening 112. Passages 118 may promote increased blood flow between
the packing material and vertebrae adjacent to implant 100. In some
embodiments, the packing material may be a pre-formed insert that
slides into opening 112.
[0040] Sides 114, 116 may include groove 120 near proximal end 122
and/or distal end 124 of body 110. Groove 120 may be designed to
receive an instrument (e.g., an implant inserter) to facilitate
insertion of implant 100 in an intervertebral disc space. Groove
120 may facilitate insertion of implant 100 using, for example, an
anterior approach, a posterior approach, or a transverse
approach.
[0041] FIG. 2 depicts a view of a posterior side of implant 100.
Distal end 124 of body 110 may be tapered and/or curved. Tapered
and/or curved surfaces of distal end 124 may facilitate insertion
of implant 100 in a disc space. In some embodiments, distal end 124
may not be tapered and/or curved. Proximal end 122 of body 110 may
be blunt and/or rounded. In some embodiments, proximal end 122 of
body 110 may have a substantially flat surface. A guide (e.g., a
tamp) or other insertion instrument may be placed against proximal
end 122 during insertion of implant 100 in a disc space using a
transverse insertion procedure. Proximal end 122 of implant 100 may
be engraved or otherwise marked with indicia to allow a user to
identify an orientation of the implant and/or one or more
properties of the implant.
[0042] FIG. 3 depicts a top view of body 110. Surfaces 126, 126',
which define opening 112 along sides 114, 116, may include one or
more projections 128, 128'. In some embodiments, projections 128,
128' may be tapered. In certain embodiments, projections 128, 128'
may be angled or rounded.
[0043] Projections 128, 128' may be located substantially
equidistant from ends 122, 124. In some embodiments, projection 128
may be closer to proximal end 122 than projection 128'. In certain
embodiments, projection 128 may be closer to distal end 124 than
projection 128'. Projections 128, 128' may strengthen implant
100.
[0044] Top and/or bottom surfaces of implant 100 may include one or
more protrusions 130, 130'. In some embodiments, one or more
protrusions 130, 130' may penetrate vertebral bone. For example, an
implant made of metal may include protrusions that are able to
penetrate vertebral bone. In some embodiments, one or more
protrusions 130, 130' may not penetrate vertebral bone. For
example, an implant made of bone may include protrusions that are
not able to penetrate vertebral bone. Protrusions 130, 130' may be
blunt, rounded, symmetrically angled, asymmetrically angled, or
pointed. The protrusions may inhibit backout of the implant from
the disc space. Protrusions 130, 130' may form a radial pattern. In
certain embodiments, protrusions 130, 130' may have a constant
height, width, and/or spacing along a length of body 110. In other
embodiments, one or more protrusions 130, 130' may have different
heights, widths, and/or spacing. For example, a width of
protrusions 130 may differ from a width of protrusions 130'.
Heights of protrusions 130, 130' may decrease or increase toward
ends 122, 124, of body 110. Spacing of protrusions 130, 130' may
increase or decrease toward ends 122, 124 of body 110.
[0045] In some embodiments, protrusions 130 on posterior side 114
may be higher and/or larger than protrusions 130' on anterior side
116. Higher and/or larger protrusions on a posterior side may allow
a greater load to be applied to posterior side 114 as implant 100
is inserted in a disc space. The greater load may facilitate proper
rotation of the implant in the disc space during insertion.
[0046] As depicted in FIG. 3, in some embodiments, implant 100 may
include course protrusions 130' near a posterior side of the
implant and fine protrusions 130 near an anterior side of the
implant. Course protrusions 130' may have greater height and/or
spacing than fine protrusions 130. In some embodiments, an implant
may include course protrusions near an anterior side of the implant
and fine protrusions near a posterior side of the implant. In some
embodiments, an implant may have the same type of protrusion
(course, fine or intermediate) near the anterior side and posterior
side.
[0047] In some embodiments, a top of an implant may have the same
types of protrusions as a bottom of the implant. In some
embodiments, the top of the implant may include different
protrusion types than the bottom. For example, the top of the
implant may include course protrusions near the posterior side,
fine protrusions near the anterior side, and the implant bottom may
include intermediate protrusions near both the anterior side and
the posterior side.
[0048] In some embodiments, top and/or bottom surfaces of a spinal
implant may be angled relative to each other to increase contact
between the implant and vertebral surfaces after insertion. Angled
top and/or bottom surfaces of an implant may help establish a
desired orientation (i.e., a proper lordotic angle) between
vertebrae that are to be fused together. Implants may be formed
with different lordotic angles. In certain embodiments, a lordotic
angle of an implant may be between about 0.degree. and about
6.degree..
[0049] Various materials may be packed in an opening of a spinal
implant. A size of an opening may facilitate insertion of materials
without adversely affecting the structural integrity of the
implant. Packing materials may include, but are not limited to,
allograft bone, bone-void filler, graft extender material,
medicine, human tissue, animal tissue, synthetic tissue, human
cells, animal cells, synthetic cells, or combinations thereof. In
some embodiments, packing material may facilitate fusion of
adjacent vertebrae with an implant.
[0050] In certain embodiments, bone may be used to form a spinal
implant. Bone used to form an implant may be, but is not limited
to, cortical, allogenic, or xenogenic bone. In some embodiments, a
portion or portions of an implant may be autogenic bone. In some
embodiments, bone, or portions of bone, used to form an implant may
be demineralized. Bone used to form a spinal implant may be
processed in a frozen state. In some embodiments, bone used to form
an implant may be processed in a freeze-dried state.
[0051] In some embodiments, a spinal implant may be constructed of
biocompatible material sufficiently strong to maintain bone
separation. An implant, or a portion of an implant, may be made of
a bioabsorbable material. For example, portions of an implant may
be made of a polyanhydride, an alpha polyester, and/or a polylactic
acid-polyglycolic acid copolymer.
[0052] In certain embodiments, a spinal implant may include one or
more inorganic compositions. For example, an implant may be made of
monocalcium phosphate, biphasic calcium phosphate,
.beta.-tricalcium phosphate, calcium metal phosphate, calcium
sulfate hemihydrate, hydroxyapatite, or combinations thereof.
Metals for a calcium metal phosphate may include, but are not
limited to, titanium, titanium alloys, and/or medical grade
stainless steel. For example, an implant may be formed of greater
than 90 wt % .beta.-tricalcium phosphate. In some embodiments, an
implant may be formed of greater than 99 wt % .beta.-tricalcium
phosphate. The use of inorganic compositions as biomaterial is
described in U.S. Pat. No. 6,537,589 to Chae et al.; U.S. Pat. No.
6,346,123 to McKay; and U.S. Pat. No. 5,717,006 Daculsi et al., all
of which are incorporated by reference as if fully set forth
herein.
[0053] In some embodiments, a spinal implant may be constructed
from bar stock or formed from moldable material of suitable
strength to withstand pressure in a normal human spine. For
example, an implant may be constructed from metals including, but
not limited to, titanium, titanium alloys, and/or medical grade
stainless steel. An implant may be molded or cut from materials
including, but not limited to, polyether ether ketone (PEEK),
carbon fiber reinforced PEEK, and other polymers.
[0054] In certain embodiments, a spinal implant and/or outer
surfaces of the implant that contact a vertebra may be made of a
material other than bone. A surface of an implant that contacts a
vertebra may be treated to enhance osseointegration of the implant
with the vertebra. The surface may include protrusions that extend
into the vertebra. The surface may include a hydroxyapatite
coating, a titanium plasma spray coating, and/or texturing.
Texturing may be used to modify the surface of an implant to reduce
expulsion and provide stability. Texturing may be provided by many
different methods, such as, but not limited to, sanding the
surface, forming grooves in the surface, shot peening the surface,
scoring the surface using an electrical discharge process, and/or
embedding hard particles in the surface. In some embodiments, an
outer surface of an implant formed of bone may be textured.
[0055] In some cases, X-rays may be used to monitor spinal fusion
in a patient. Some implant embodiments (e.g., PEEK implants) are
substantially transparent to X-rays. X-ray detection of an implant
formed of X-ray transparent material may be facilitated by
including X-ray sensitive material in the implant. FIG. 2 depicts
implant 100 with openings 132 for X-ray sensitive material. In an
embodiment, tantalum wire (e.g., 1 mm in length) may be inserted
into one or more openings 132 of implant 100 before implantation.
In some embodiments, X-ray sensitive material may be located near
an anterior side of the implant adjacent to a caudal (or cephalic)
surface of the implant. X-ray sensitive material may also be
located near a posterior side of the implant adjacent to a cephalic
(or caudal) surface of the implant. The use of X-ray sensitive
material in an implant may allow a location of the implant to be
visualized after insertion using X-ray imaging.
[0056] Bone growth that fuses vertebrae together through an implant
may be monitored subsequent to an implant insertion procedure. Bone
growth in an implant that is not X-ray transparent (e.g., a
metallic implant) may be monitored in a passage or an opening of
the implant. For example, an X-ray image may indicate the presence,
absence, and/or density of bone in passages 118 of implant 100.
[0057] X-ray and/or other imaging techniques may be used to
determine a height and/or lordotic angle of an implant suitable for
an implant insertion procedure. Implants that will provide the
desired height and/or lordotic angle may be included with an
instrumentation set for the implant insertion procedure. Implants
with various heights and/or lordotic angles may be included with an
instrumentation set to allow a range of options during a surgical
procedure.
[0058] An instrumentation set may include instruments used to
insert an implant in a disc space. Instruments used during implant
insertion may allow positioning and/or manipulation of an implant
to be affected from above an incision in a patient. The instruments
may allow simple, efficient, and safe insertion of an implant. In
some embodiments, an implant may be inserted in a disc space
between adjacent vertebrae. In certain embodiments, an implant may
be inserted in a space formed between two portions of a bone to
extend the length of the bone. The instruments may allow implant
insertion through a relatively small incision in a patient, while
maintaining ample visibility of the surgical site, implant, and
instruments during the procedure.
[0059] An instrumentation set for a spinal implant insertion
procedure may include various instruments for distraction, disc
preparation, and implantation. The distraction instruments may
include fixed-tip and/or removable-tip distractors. Disc
preparation instruments may include, but are not limited to,
cutting distractors, rasps, curettes, rongeurs, chisels, and/or
retractors. Implantation instruments may include implant inserters,
mallets, one or more guides, and/or funnels.
[0060] FIG. 4 depicts an embodiment of fixed-tip distractor 134.
Distractor 134 may be used to separate vertebrae during an
insertion procedure. Distractor 134 may include tip 136 and shaft
138. Tip 136 may be fixed to shaft 138. Shaft 138 may include
indicia 146. Indicia 146 may indicate an insertion depth of tip 136
in a disc space. Shaft 138 may include flat 140 and connector 142.
End 148 of connector 142 may have a cross-sectional shape similar
to that of shaft 138. In some embodiments, end 148 may be a collar
coupled to connector 142. Connector 142 may have a cross-sectional
shape that is substantially the same as, but slightly smaller than,
a cross-sectional shape of an opening in a removable handle. A
removable handle (e.g., a T-handle) may fit over connector 142 and
mate with flat 140 such that rotation of the handle results in
rotation of tip 136. In some embodiments, shaft 138 may include a
release and a detent that couples with an indention of a removable
handle.
[0061] FIG. 5 depicts a side view of tip 136 of distractor 134. In
some embodiments, tip 136 may have a narrow dimension and a wide
dimension. The narrow dimension may be substantially perpendicular
to the wide dimension. Surfaces 150, 150' may define the narrow
dimension of tip 136. Surface 150 may taper toward surface 150'. In
some embodiments, surface 150' may taper toward surface 150. The
distal end of tip 136 may narrow progressively, such that the
distal end of the tip is the narrowest portion of the tip.
[0062] FIG. 6A depicts an end view of tip 136 of a distractor. Tip
136 may include curved surfaces 154. Curved surfaces 154 may be
proximate tapered surfaces 150, 150'. A tip with a curved surface
may rotate more easily in a disc space than a tip with a flat
surface, thereby reducing trauma to the patient.
[0063] Surfaces 156 of tip 136 may define a wide dimension of tip
136. The wide dimension may be substantially constant along a
length of the tip. The wide dimension may correspond to the desired
separation distance to be established by the distractor between
adjacent vertebrae. The desired separation distance may be, for
example, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, or 13 mm.
Edges 160 of tip 136 may be rounded to facilitate rotation of the
tip between vertebrae. In some embodiments, tip 136 may be used to
sever tissue (e.g., disc tissue). As depicted in FIG. 6B, tip 136
may include cutting surfaces 162 for severing tissue.
[0064] A removable handle may be may attached to shaft 138 of
distractor 134. The handle may be coupled substantially parallel to
the wide dimension of tip 136. The handle may be oriented
perpendicular to a patient's spinal column, such that the narrow
dimension of the tip is substantially perpendicular to the spinal
column. The handle may be rotated approximately 90.degree., such
that the handle and the wide dimension of tip 136 are substantially
aligned with the spinal column. The wide portion of tip 136 may
establish a desired separation distance between vertebrae. After
distraction of the vertebrae, the handle may be removed from shaft
138.
[0065] Vertebral surfaces may require preparation before insertion
of an implant in a disc space. Vertebral surfaces may be abraded to
remove osteophytes and/or to smooth rough surfaces. An instrument
such as a rasp may be inserted in an intervertebral disc space from
a posterior or transverse approach to abrade vertebral
surfaces.
[0066] FIG. 7 depicts a front view of rasp 164 that may be used to
abrade vertebral surfaces. Rasp 164 may include end member 166,
inner shaft 168, outer shaft 170, locking member 172, and handle
174. End member 166 may couple to inner shaft 168. Inner shaft 168
may be coupled to handle 174. Outer shaft 170 may have a
cross-sectional shape substantially the same as, but slightly
larger than, a shape of inner shaft 168. Inner shaft 168 may
translate relative to outer shaft 170. Outer shaft 170 may include
indicia 146 to indicate insertion depth of end member 166 during
use.
[0067] FIG. 8 depicts a perspective view of end member 166. A shape
of end member 166 may be chosen to promote contact of rasp 164 with
adjacent vertebrae. In some embodiments, a shape of end member 166
may be chosen to substantially match a shape of an implant. A
cross-sectional shape of end member 166 may be, but is not limited
to, oval, elliptical, circular, square, rectangular, or irregular.
In certain embodiments, end member 166 may be kidney shaped. A
height of end member 166 may be chosen to match a height of an
implant to be inserted. For example, a height of end member 166 may
be about 9 mm, about 11 mm, or about 13 mm. End member 166 may
include opening 176. Inner shaft 168 may extend through opening 176
and couple with end member 166. End member 166 may include various
configurations for coupling to inner shaft 168 (e.g., threads,
pins, solder). For example, pin 178 may couple end member 166 to
inner shaft 168.
[0068] Surfaces of end member 166 may be textured to abrade and/or
cut vertebral bone. Texturing may be provided by methods including,
but not limited to, sanding the surface, forming grooves in the
surface, shot peening the surface, scoring the surface using an
electrical discharge process, and/or embedding hard particles in
the surface.
[0069] Rotation (e.g., clockwise rotation) of locking member 172
may allow outer shaft 170 to engage end member 166. In certain
embodiments, rotation of locking member 172 may allow a biasing
member to drive outer shaft 170 toward end member 166. The biasing
member may be, but is not limited to, a spring, a spring mechanism,
and/or an elastomer. Distal end 180 of outer shaft 170 may engage
end member 166 to hold the end member in position at an initial
angle relative to inner shaft 168. Distal end 180 may include
various configurations (e.g., grooves and ridges, detents and
indents, openings and protrusions, or threads) to engage end member
166. For example, edges of end member 166 and distal end 180 may
include complementary ridges and grooves that engage when aligned.
In other embodiments, end member 166 may include indents or slots
that engage detents or pins of distal end 180. In certain
embodiments, distal end 180 may include indents that engage detents
of end member 166.
[0070] Rotation of locking member 172 in an opposite direction
(e.g., counterclockwise) may release distal end 180 from end member
166. In certain embodiments, releasing locking member 172 may
release a biasing member holding distal end 180 against end member
166. Release of the biasing member may release distal end 180 from
end member 166. With distal end 180 released from end member 166,
handle 174 may be used to pivot end member 166 relative to inner
shaft 168. FIG. 9 depicts rasp 164 with end member 166 angled
relative to inner shaft 168. After positioning of end member 166,
locking member 172 may be engaged to secure a position of end
member 166 relative to inner shaft 168. An angle of end member 166
relative to inner shaft 168 may be adjusted to range from about
0.degree. to about 90.degree.. In some embodiments, an angle of end
member 166 relative to inner shaft 168 may be about 45.degree.
during use. In other embodiments, an angle of end member 166
relative to inner shaft 168 may be about 30.degree. during use. In
certain embodiments, an angle of end member 166 relative to inner
shaft 168 may be about 60.degree. during use. An angle of end
member 166 relative to inner shaft 168 may allow rasp 164 to be
inserted in a disc space during a transverse approach. After
insertion, end member 166 may be pivoted to allow rasp 164 to be
maneuvered in the disc space. End member 166 may be pivoted and
locked in various angles relative to inner shaft 168 while in the
disc space to abrade vertebral surfaces.
[0071] Rasp 164 may be advanced in a disc space to abrade vertebral
surfaces. Abrasion of vertebral surfaces may be performed by moving
handle 174 of rasp 164. Handle 174 may include grips and/or a
textured surface. A proximal end of handle 174 may include an
attachment for a drive instrument (e.g., a slap hammer). In certain
embodiments, handle 174 may be removable from inner shaft 168 of
rasp 164.
[0072] An instrument guide may be used to facilitate positioning of
an implant in a prepared disc space. FIG. 10 depicts a perspective
view of an embodiment of instrument guide 182 that may be used to
guide an implant in a disc space. Guide 182 may include end member
184, shaft 186, and handle 188. A height of end member 184 may
complement a size of implant 100. A shape of end member 184 may be
curved to help maneuver an implant in a disc space. In some
embodiments, a cross-sectional shape of end member 184 may be
curved.
[0073] End member 184 may couple to shaft 186. A height and shape
of shaft 186 and handle 188 may facilitate positioning guide in a
desired location while keeping the handle out of the way when end
member 184 is properly positioned. Shaft 186 may be curved near
handle 188 to enable an implant inserter and/or other instrument to
be positioned proximate guide 182. Shaft 186 may include indicia
146 to indicate an insertion depth of end member 184.
[0074] An implant inserter may be used to position an implant in a
disc space. In some embodiments, the implant inserter may be used
to grasp side surfaces of an implant. An implant designed to be
grasped from the side may have a solid end. An implant with a solid
end may be structurally strong enough to withstand forces that may
break or fracture implants with an opening in an end. The use of an
implant inserter to grasp side surfaces of an implant may avoid
application of rotational forces to the implant during removal of
the implant inserter.
[0075] FIG. 11 depicts an embodiment of implant inserter 190 that
may be used to insert implant 100 in a prepared disc space. Implant
inserter 190 may advantageously have a low profile. An implant
inserter with a low profile may allow a surgeon to see a surgical
site during an implant insertion procedure. Implant inserter 190
may include arms 192, outer shaft 194, locking member 196, inner
shaft 198, and handle 200. Arms 192 may couple to inner shaft 198.
Outer shaft 194 may have a cross-sectional shape that is
substantially the same as, but slightly larger than, a shape of
inner shaft 198. Inner shaft 198 may rotate and/or translate in
outer shaft 194. Inner shaft 198 may be fixed to handle 200.
Proximal end of handle 200 may include an attachment for a drive
instrument (e.g., a slap hammer) used during insertion of an
implant in the disc space. In some embodiments, handle 200 may be
removable from inner shaft 198.
[0076] Grasping portions of arms 192 of implant inserter 190 may be
wider than other portions of the arms. Arms 192 may grasp recesses
or grooves (e.g., grooves 120 of implant 100 depicted in FIG. 1) of
an implant positioned between the arms. Arms 192 may be roughened,
grooved, knurled, shot peened, chamfered, or otherwise textured to
promote contact between the implant and the arms.
[0077] Rotation (e.g., clockwise rotation) of locking member 196
may drive outer shaft 194 toward an implant positioned between arms
192. In certain embodiments, rotation of locking member 196 may
allow a biasing member to drive outer shaft 194 toward an implant
positioned between arms 192. An end of outer shaft 194 may contact
wide portions of arms 192 to hold the implant between the arms, as
depicted in FIG. 13A. Rotation of locking member 196 in an opposite
direction (e.g., counterclockwise) releases outer shaft 194 and
allows arms 192 to separate, thereby releasing the implant. In
certain embodiments, rotation of locking member 196 may release a
biasing member. Release of the biasing member may release outer
shaft 194 and allow arms 192 to separate, thereby releasing the
implant.
[0078] After an implant has been released from implant inserter
190, instrument guide 210 may be used to position the implant. FIG.
12 depicts an embodiment of guide 210. Guide 210 may include tip
212, shaft 214, and handle 216.
[0079] A distal end of tip 212 may have a cross-sectional shape
characterized by a narrow dimension and a wide dimension. The
narrow dimension and the wide dimension may be substantially
perpendicular to each other. Tip 212 may be tapered at the distal
end in the narrow dimension. Tip 212 may be curved in the wide
dimension. A curve in the wide dimension of the tip may complement
a rounded edge of an implant. The curvature of tip 212 may be used
to help guide the implant into position during a transverse
approach.
[0080] Handle 216 may be coupled to shaft 214. The proximal end of
handle 216 may include strike surface 218. A mallet or other impact
tool may be used to hit strike surface 218 during insertion of an
implant. Strike surface 218 may be located substantially directly
over an implant to distribute a force across the implant surface.
In some embodiments, a portion of strike surface 218 may be located
above a corner of implant 100 to facilitate proper positioning of
the implant during use.
[0081] A spinal implant may be inserted in an intervertebral disc
space using a minimally invasive approach or a traditional surgical
approach (e.g., transverse, posterior, anterior). A transverse
approach may involve removal of a portion or the entire facet joint
unilaterally. In some embodiments, a port may be inserted into a
patient to provide access to vertebrae that are to be fused
together. Instruments (e.g., distractors, chisels, size trials,
implant inserters) may be inserted into the port during an implant
insertion procedure.
[0082] Portions of bone and/or other material may be used to form a
spinal implant designed to fuse two vertebrae together. The
resulting implant may be provided with a desired lordotic angle
and/or texturing that inhibits backout of an implant from a disc
space. If an implant is formed of bone, the implant may be
processed in a freeze-dried state. Before insertion into a patient,
a freeze-dried implant may be reconstituted by soaking the implant
in an aqueous solution.
[0083] During an insertion procedure, disc material may be removed
to form a disc space. An implant may be inserted in the disc space.
In a posterior procedure, an incision may be made and portions of a
lamina or spinous process may be removed to provide access to the
disc. The spinal cord or cauda equina may be retracted.
[0084] In a transverse approach, a portion of a facet joint may be
removed. An implant that spans an intervertebral disc space may be
inserted in the disc space. Insertion of an implant using a
transverse approach may maintain healthy anatomical structure of
the vertebrae on the contralateral side. In some embodiments a
pedicle screw and rod construct may be applied to the same side or
on opposite sides of an implant to strengthen the implant.
[0085] A discectomy may be performed to remove disc material from a
disc space. A distractor, such as distractor 134 depicted in FIG.
4, may be positioned in the disc space to establish a separation
distance between the vertebrae. A disc space may be prepared using
instruments such as, but not limited to, curettes, chisels, or
rongeurs. A chisel may be used to remove portions of vertebral bone
and form channels in the vertebral end plates adjacent to the disc
space.
[0086] A rasp, such as rasp 164 depicted in FIG. 7, may be used to
remove disc material and roughen the vertebral endplates, allowing
for improved vascularity of the bony mass. End member 166 may be
angled relative to inner shaft 168 of rasp 164 in the disc space to
prepare the disc space from a unilateral approach. A size of rasp
164 may be used to select a size of an implant to be inserted.
[0087] FIGS. 13A-13C depict insertion of implant 100 in a prepared
disc space. An implant, such as implant 100 depicted in FIGS. 1-3,
may be attached to an implant inserter, such as implant inserter
190 depicted in FIG. 11. A guide, such as guide 182 depicted in
FIG. 10, may be inserted in the prepared disc space. In some
embodiments, a portion of guide 182 may be equal in size to implant
100. Implant 100 may be placed proximate guide 182, as depicted in
FIG. 13A. Implant 100 may be positioned along end member 184 of
guide 182 until the implant is proximate the curved portion of the
end member. Implant 100 may be released from implant inserter
190.
[0088] A guide, such as guide 210 depicted in FIG. 12, may be
inserted into the disc space. Guide 210 may be placed proximate a
proximal end of implant 100 as depicted in FIG. 13B. As shown in
FIG. 13C, guides 210, 182 may be used in concert to guide, turn,
and/or position implant 100 in the prepared disc space. A strike
instrument may be used with guide 210 to move the implant along end
member 184 of guide 182. FIG. 13D depicts implant 100 after removal
of the guides from the disc space.
[0089] In this patent, certain U.S. patents have been incorporated
by reference. The text of such U.S. patents is, however, only
incorporated by reference to the extent that no conflict exists
between such text and the other statements and drawings set forth
herein. In the event of such conflict, then any such conflicting
text in such incorporated by reference in such U.S. patents is
specifically not incorporated by reference in this patent.
[0090] Further modifications and alternative embodiments of various
aspects of the invention will be apparent to those skilled in the
art in view of this description. Accordingly, this description is
to be construed as illustrative only and is for the purpose of
teaching those skilled in the art the general manner of carrying
out the invention. It is to be understood that the forms of the
invention shown and described herein are to be taken as the
presently preferred embodiments. Elements and materials may be
substituted for those illustrated and described herein, parts and
processes may be reversed, and certain features of the invention
may be utilized independently, all as would be apparent to one
skilled in the art after having the benefit of this description of
the invention. Changes may be made in the elements described herein
without departing from the spirit and scope of the invention as
described in the following claims.
* * * * *